Turbine flowmeter is generally composed of two parts: sensor and display instrument.

Turbine flowmeter, volumetric flowmeter and coriolis mass flowmeter are called the three types of repeatable flowmeters, as the ten types of flowmeters, their products have been developed for multi-variety, multi-series of mass production scale.

When the flow rate is greater than the initial flow rate, the turbine flowmeter turbine rotation angular velocity will increase with the increase of the flow rate.In the measurement range, the resistance moment T generated by the fluid will become the main factor affecting the characteristics of the flow meter.In contrast, the friction of bearings and other mechanical transmission components produces a relatively small mechanical resistance moment.In the following discussion, assuming that the mechanical resistance moment is 0, the instrument coefficient: K= b-c [T/ Q2] (1)B, C -- constants.The laminar flow state and turbulent flow state will be discussed respectively because the mechanism and effect of fluid resistance are different in different flow states.To distinguish laminar flow state from turbulent flow state, the concept of Reynolds number (Re) must be introduced.D -- pipe diameter;-- the kinematic viscosity of the fluid in the tube.Generally, Re≥2320 is the judgment basis for the transition from laminar flow to turbulent flow.In the laminar flow state, the resistance moment T of the fluid flow is proportional to the fluid dynamic degree (also known as viscosity) and the fluid flow rate Q, that is, T=C1μQ.Where, C1 is a constant, and substituted into equation (1), it can be seen that: if the viscosity changes, the instrument coefficient K also changes;If the viscosity doesn't change.Then K will increase with the increase of traffic.When the turbine flowmeter is in a turbulent flow state, the fluid flow resistance moment T is proportional to the fluid density and Q2.The effect of fluid viscosity can be calculated.In this equation, C2 is a constant. By substituting into equation (1), it can be seen that: in the turbulent flow state, the instrument coefficient K is only related to the structure parameters of the instrument itself, and has nothing to do with parameters such as flow Q and fluid viscosity, and can be approximated as a constant.Only in this state does the instrument coefficient K really show the properties of the constant.The interval where the meter coefficient K is constant is the measurement range of the turbine flowmeter.